The present invention relates generally to photography.
Image blur is a common problem in photography. Some common causes of blur in a photograph are subject motion, camera motion (shake), and focusing errors. Blur is a particular problem for casual or amateur photographers who may not know how to diagnose the causes of blur or how to change their photographic technique to improve their results. As new consumer camera models are being produced with zoom lenses capable of very long focal lengths, blur due to camera shake is especially troublesome.
Some simple approaches to reducing blur resulting from camera shake include placing the camera on a tripod, and using a faster shutter speed. However, a tripod may not be readily available or convenient in a particular photographic situation. Using a faster shutter speed is not always feasible, especially in situations with dim lighting. Shutter speed may be increased if a larger lens aperture is used, but larger-aperture lenses arc bulky and expensive and not always available. In addition, the photographer may wish to use a smaller lens aperture to achieve other photographic effects such as large depth of field.
Various devices and techniques have been proposed to help address the problem of image blur due to camera shake. For example, Murakoshi (U.S. Pat. No. 4,448,510) uses an accelerometer to detect camera shake, and provides an indication to the user of the camera if the acceleration exceeds a threshold level. The photographer can then make appropriate adjustments.
Satoh (U.S. Pat. No. 6,101,332) also senses camera shake, and combines the shake information with other camera parameters to estimate how much image blur might result. A set of light emitting diodes communicates the estimate to the photographer, who can then make adjustments.
Another approach has been to automate the camera operation, and let the camera choose settings that will minimize blur. For example, Bolle et al. (U.S. Pat. No. 6,301,440) applies a variety of image analysis techniques in an attempt to improve several aspects of photographs.
Some cameras or lenses are equipped with image stabilization mechanisms that sense the motion of the camera and move optical elements in such a way as to compensate for the camera shake. See for example Otani et al. (U.S. Pat. No. 5,774,266) and Hamada et al. (U.S. Pat. No. 5,943;512).
Each of these approaches has its drawbacks. The above techniques may require the addition of expensive and delicate electro-mechanical components to a camera, thereby increasing the camera cost. The techniques may require knowledgeable intervention from the photographer, possibly requiring equipment that is not at hand. Additional automation that reduces the photographer""s control of the camera may add to the mystery of why a particular photograph is blurred.
A solution to the problem of image blur is needed that also addresses these difficulties.
A camera measures camera motion. Near the time of taking a photograph, the camera uses an actuator to accelerate an inertial element in a direction that counters the motion of the camera. The direction and duration of the acceleration are selected to momentarily reduce the camera rotation so that a photograph may be taken while the camera is relatively stable. Energy for actuating the inertial element may be stored in a capacitor. Several example means of monitoring the camera motion are disclosed, including an accelerometer, a rate gyroscope, and analysis of successive digital images. The inertial element may optionally be the rotor of a motor. The inertial element may optionally be the core of a solenoid. The camera may optionally use multiple actuators and masses to control shake in more than one degree of freedom. Methods of adapting the system to camera panning are disclosed.